• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.4 s.247
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• pp.379-386
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• 2006

The hyper-elastic material has been used gradually and its range was extended all over the industry. The performance prediction of hyper-elastic material was required not only experimental methods but also numerical methods. In this study, we presented the process how to use numerical method for hyper-elastic material and applied it to seat-ring of butterfly valve. The finite element analysis was executed to evaluate the mechanical characteristics of hyper-elastic material. And the optimum model considered conditions and features. According to that model, the load conditions were obtained by using CFD analysis.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.2
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• pp.144-154
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• 1998

A functionally graded material is a nonhomogeneous material, which is composed of several different materials to maintain structural rigidity and endure high temperature loads. An analytical method is presenter to solve the unsteady heat conduction equation for nonhomogeneous materials. A one-dimensional infinite plate made of functionally graded material is considered. The approximate Green's function solution is derived and to be used to obtain the temperature distribution them the stress distributions may be obtained. The volume fraction, the porosity, the stress difference, and the stress ratio are the design parameters and are to be used to set up a systematic design procedure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.11
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• pp.693-698
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• 2017

In this study, the thermal degradation properties of polyethylene terephthalate film has been examined by the capacitance, Tan ${\delta}$, thermography, FTIR, and SEM results at temperatures of $90{\sim}170^{\circ}C$ and frequencies of 0.3~3,000 kHz. It was found that the capacitance decreased with increasing thermal imaging temperature, probably caused by weakening of chemical bond with increasing temperature. Tan ${\delta}$ decreased upon increasing temperature from $90^{\circ}C$ to $170^{\circ}C$, probably due to the molecular motion of COOH radical or OH radical. The FT-IR measurement reveals that no structural change of the material occurs upon thermal radiation. The SEM measurement shows that the material is stabilized by thermal decomposition with increasing temperature; however, excessive thermal degradation obstructs the stabilization of the material.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.605-610
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• 2002

Eigenvalues are taken as performance criteria for structural damping design using viscoelastic material. Given material properties, optimal distribution of damping material is sought based on eigenvalue sensitivity. For eigenanalysis of frequency dependent viscoelastic material treated structures, Golla-Mushes-McTavish (GHM) model is used and some dominant modes are chosen for consideration. To avoid the intensity of computation caused by increased problem size, an alternative approximate method is proposed which uses elastic modes and can be applied under small damping assumption. A cantilever beam treated with unconstrained viscoelastic layer is tested and optimal distribution of thickness of the layer is illustrated. Partial coverage configurations are compared with the one-sided full coverage case.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.16 no.4
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• pp.26-34
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• 2008

This article provides a comprehensive treatment of cracks in non-homogeneous structural materials such as functionally graded materials (FGMs). It is assumed that the material properties depend only on the coordinate perpendicular to the crack surfaces and vary continuously along the crack faces. By using laminated composite plate model to simulate the material non-homogeneity, we present an algorithm for solving the system based on Laplace transform and Fourier transform techniques. Unlike earlier studies that considered certain assumed property distributions and a single crack problem, the current investigation studies multiple crack problem in the FGMs with arbitrarily varying material properties. As a numerical illustration, transient thermal flow intensity factors for a metal-ceramic joint specimen with a functionally graded interlayer subjected to sudden heating on its boundary are presented. The results obtained demonstrate that the present model is an efficient tool in the fracture analysis of non-homogeneous material with properties varying in the thickness direction.

• Structural Engineering and Mechanics
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• v.58 no.2
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• pp.217-230
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• 2016

Effects of temperature dependent material properties on mixed mode fracture parameters of functionally graded materials subjected to thermal loading are investigated. A domain form of the $J_k$-integral method including temperature-dependent material properties and its numerical implementation using finite element analysis is presented. Temperature and displacement fields are calculated using finite element analysis and are used to compute mixed mode stress intensity factors using the $J_k$-integral. Numerical results indicate that temperature-dependency of material properties has considerable effect on the mixed-mode stress intensity factors of cracked functionally graded structures.

• Structural Engineering and Mechanics
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• v.24 no.1
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• pp.31-50
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• 2006

This paper deals with the mechanical behaviour of the thin-walled cylindrical air-spring shell (CAS) made of rubber-textile cord composite (RCC) subjected to different types of loading. An orthotropic hyperelastic constitutive model is presented which can be applied to numerical simulation for the response of biological soft tissue and of the nonlinear anisotropic hyperelastic material of the CAS used in vibroisolation of driver's seat. The parameters of strain energy function of the constitutive model are fitted to the experimental results by the nonlinear least squares method. The deformation of the inflated CAS is calculated by solving the system of five first-order ordinary differential equations with the material constitutive law and proper boundary conditions. Nonlinear hyperelastic constitutive equations of orthotropic composite material are incorporated into the finite strain analysis by finite element method (FEM). The results for the deformation analysis of the inflated CAS made of RCC are given. Numerical results of principal stretches and deformed profiles of the inflated CAS obtained by numerical deformation analysis are compared with experimental ones.

• Journal of Aerospace System Engineering
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• v.10 no.1
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• pp.103-110
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• 2016

This study shows the statistical properties of the domestic composite material prepregs test result. During the last three years(2012.5~2015.6) the prepreg specimen tests have been performed by referring to NCAMP developed test procedure which was approved by FAA. The database of (1) Carbon Tape, (2) Glass Fabric, and (3) Carbon Fabric composite material prepregs' characteristics have been established for certified aircraft structures. This qualified materials can be used for aircraft structural design through proper material equivalency procedures.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.693-705
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• 2016

Functionally graded material (FGM) plates can be bonded to the soffit of a beam as a means of retrofitting the RC beam. In such plated beams, tensile forces develop in the bonded plate and these have to be transferred to the original beam via interfacial shear and normal stresses. In this paper, an interfacial stress analysis is presented for simply supported concrete beam bonded with a functionally graded material FGM plate. This new solution is intended for application to beams made of all kinds of materials bonded with a thin plate, while all existing solutions have been developed focusing on the strengthening of reinforced concrete beams, which allowed the omission of certain terms. It is shown that both the normal and shear stresses at the interface are influenced by the material and geometry parameters of the composite beam. This research is helpful for the understanding on mechanical behavior of the interface and design of the FGM-RC hybrid structures.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.523-525
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• 2002

The poly-Si thin film can be used in high mobility active matrix liquid-crystal display (AMLCD) and system on panel (SOP). In this paper, poly-Si thin films were grown by novel high temperature process on the molybdenum (Mo) substrate. By applying a high current above 48A on a Mo substrate. We obtained an improved crystalline Si films with the crystallinity over 80%. We exhibit the properties of structural and electrical properties of high temperature poly-Si thin film transistor on the Mo substrates.